This invention relates to a multi-product fuel dispenser and, more particularly, to such a dispenser that feeds more than one product through an ultrasonic metering device and a single hose and nozzle.
Many gasoline service stations require the installation of multi-product fuel dispensers or pumps, each for dispensing a plurality of different grades, or octane levels, of gasoline products at each fueling station. Conventionally, three different products are provided per fueling station, namely a high octane fuel, a medium octane fuel and a low octane fuel. In the past, multi-product dispensers had a separate hose for each product. Now, many such dispensers use the same hose and nozzle to dispense all products. Mixing of these various products can result in the dilution or lowering of the octane level of the high and medium octane fuels which can lower the octane level of the fuel delivered to the customer. Testing procedures have therefore been developed in the United States to certify the octane levels of the fuels dispensed from commercial fuel dispensers. The testing and certification procedures are set forth in the National Conference on Weights and Measures Publication No. 12, entitled "Examination Procedure Outlines for Weighing and Measuring Devices." Pursuant to these testing guidelines, the person conducting the test is required to flush at least 0.3 gallons of fuel from the dispenser before taking the test sample. See page 57, line 1. Thus, in dispensers used at United States gasoline service stations, a slight mixing of the various fuel products of a multi-product fuel dispenser may occur, so long as the contaminated product is flushed from the system during the first 0.3 gallons of discharge.
To avoid the mixing of the various products dispensed from a multi-product fuel dispenser, known dispensers typically include a separate flow path for each product from its reservoir product tank which stores the fuel, to the outlet nozzle which introduces the fuel into the consumer's automobile. These systems therefore require the duplication of the components disposed between the tank and the nozzle for each fuel product, including the flow meter. In this manner, however, no contamination of the octane level of the products can occur. Through the use of such separate hoses, meters, etc., dispensers of the prior art avoid contamination of fuel being dispensed at a particular time, with fuel from a previous use that would otherwise remain in the system at the termination of the last dispensing cycle. Spalding, U.S. Pat. No. 5,332,011, a patent assigned to the assignee of the present invention, discloses such a dispenser, in which three nozzles, fuel hoses and flow meters, each for a different grade of gasoline, are combined in a single dispenser.
There are many disadvantages in the use of discrete delivery systems for each product fed through a multi-product fuel dispenser. For example, the cost of such dispensers is increased due to the requirement for multiple hoses, nozzles and meters. Also, the overall size and space requirements of such a dispenser are increased due to the requirement to house the multiple components. In addition, and especially with respect to the flow meters, the cost of maintenance and repairs is increased for each discrete delivery system included in such dispensers.
Other multi-product fuel dispensers have been developed in which the supply lines from each reservoir tank are manifolded into a single fuel hose downstream of the flow meter, which hose then leads to a single nozzle. Although this eliminates the cost of the multiplicity of nozzles and hoses, the problems associated with the multiplicity of flow meters, such as complexity, space limitations and repair and maintenance expenses, remain.
In one known device, different grades of fuel from three different storage sources can be delivered through a common meter and then dispensed through a dedicated hose and nozzle for each fuel grade. A specific valving arrangement controls the flow of a specific fuel grade through the meter and to the dedicated hose and nozzle. As an alternative, different grades of fuel from three different storage sources can be delivered through a common meter and then selectively dispensed through a single hose and nozzle. In this arrangement, valving selectively directs a specific fuel grade to the common meter and the meter is connected to the single hose and nozzle.
In another arrangement, fuel delivery of various grades, through a single hose and nozzle, is accomplished from two different grades of fuel (i.e., highest octane and lowest octane) stored separately. Here again, a specific valving arrangement controls the delivery of the selected fuel grade. The separately stored fuels may be blended to deliver one or more intermediate grades of fuel. This may be accomplished by proportional blending or fixed ratio blending. In proportional blending, various intermediate grades are a selectively blended mixture of some proportion of the high and low octane fuels. In fixed ratio blending, a single intermediate grade is produced including a fixed percentage of the high and low octane fuels.
In all blending dispensers there are two separate sets of hydraulics. One set is for controlling the low octane product input and another set is for controlling the high octane product input. In blending dispensers, whether of the proportional or fixed ratio type, the low and high octane hydraulic systems each contain a proportional flow control valve.
When any grade (low, high or blend) is selected, the blend ratio programmed into the dispenser's computer determines the percentage or proportion of high product to be dispensed. When the low grade product is selected, the proportion or percentage of high product is 0%. When the high grade product is selected, the percentage of high product is 100%. When a blended grade is selected, a percentage of high product (less than 100%) is mixed with the remaining percentage of low product, and the combined total (100%) determines the octane rating of the blended grade.
Knowing the percentage or proportion of high, and thus low, product to dispense and by calculating the volume dispensed based on input signals from the pursers, the computer signals the solenoid drive board which in turn controls the proportional flow control valves. Each proportional flow control valve continuously opens or closes, as directed by the solenoid drive board, to maintain the desired blend ratio and the maximum allowable flow rate.
A complication arises with regard to the allowable 0.3 gallon contamination factor. Some gasoline station operators would prefer to have a dispenser hose provided with a greater than normal length. The normal hose length provided is about 12 feet. The volume of fuel retained in a 12 foot length of hose and the volume of fuel in the flow meter approximates the allowable 0.3 gallon contamination factor. Therefore, extending the hose length to, for example, 13 feet may cause the system to exceed the 0.3 gallons of allowable contamination due to the increased volume of the extended length of the hose.
In Europe, the 0.3 gallon contamination factor is generally not permitted. In fact, only the minimal nozzle volume contamination is permitted. Therefore, separate nozzles and hoses are required for each grade of fuel product. In one attempt to overcome some of the above problems, however, multi-product fuel dispensers have been developed that comprise tri-axial fuel hoses having three concentric passages within a single hose that lead to a single nozzle. Such devices simplify operation for the consumer as there is only a single nozzle, but they do not alleviate the need for separate flow meters for each product or improve the maintenance and repair costs. Moreover, such devices might actually increase the cost of the dispenser due to the complexity of the tri-axial hoses.
The present meters include a mechanical positive displacement meter using technology which is over 50 years old. This meter includes over 100 parts, is cumbersome, not service friendly, and not easily interfaced with modern microprocessor based control systems. Although some electronic flow sensing devices have been recently introduced, present meters are of too large a volume, e.g., in excess of about 0.1 gallons, which is one-third of the permissible 0.3 gallons. Volume of these meters is large to produce the desired system flow rate of 10 gallons per minute (gpm). This means that the other components of the system which contribute to product contamination must be limited to no more than 0.2 gallons.
More recently, a multiple compartment hose has been developed. One compartment carries a low octane product, another compartment carries a high octane product and a third compartment is for vapor recovery. This, permits single hose dispensing using a nozzle with a blend valve. One such nozzle has been developed including an in line flow meter, valve and check valve arrangement. However, the proposed flow meter is described as a turbine flow meter. Adding these features to the nozzle will add size and weight to the nozzle. In addition, a multiple compartment hose may include separate compartments for delivering three grades of fuel and a fourth compartment for vapor recovery in a non-blending system.
Therefore, what is needed is an economically feasible meter of smaller volume, i.e., substantially less than 0.1 gallons, able to operate within a nozzle in combination with a three compartment hose and a blend valve in the nozzle at the system flow rate of 10 gpm, reliable due to few or no moving parts, and capable of almost infinite life.